A chairde,
There's a new Yahoo group (
http://groups.yahoo.com/group/firststepsinirish) which will begin studying Irish on 28 August 2007 using the coursebook "First Steps in Irish", by the Christian Brothers. This book is a grammar-based graded course suitable for beginners/revision, and available from such dealers as litriocht.com, ossianusa.com or cuplafocal.ie.
Although FSII as originally published lacks answer keys and audio material, such resources can now be downloaded from this website:
http://fsii.gaeilge.org